In many homes, it is common for floors to start to sag after a while.
This common occurrence usually is not something to be worried about. However, if the floors are sagging too much, it could be a problem.
Most of the time, when floors are sagging, it is because the joists have become worn out. As the wood ages, it will lose some of its strength and will bend when you walk on it.
Fortunately, there are ways to fix this. By strengthening the joists from beneath, you can make sure your floors are safe and secure.
Strengthening Floor Joists From Beneath: Basic Idea
There are a few different methods available for strengthening floor joists from beneath. These include:
- Reinforce with plywood
- Apply blocking
- Use steel
- Add a joist beam
Why Strengthen Floor Joists?
If you have a basement or crawlspace under your home, you may experience floor sagging. When this happens, the floor can feel unsteady or less secure than it should.
If you have a basement, a sagging floor means that the joists holding it up are weakening. This could potentially lead to someone falling through the floor.
If you want to make sure that your home is safe and secure, strengthening the joists is a good option.
In many municipalities, it is against building codes to have sagging floors.
A building inspector will want to make sure that any home is safe for all kinds of people. If they find out your joists are weak, you could end up getting a fine.
Add Plywood Reinforcements
One of the simplest ways of strengthening floor joists is reinforcing them with plywood.
¾” plywood is the best material to use for this method and will ensure a strong bond. It is also widely available and relatively inexpensive compared to other methods.
In most homes, there will be a top and bottom beam holding up the floor. Rip the ¾” plywood to the same width of those joists.
Then, lift the joists up to the height you need them to be. This can be done with a jack or cinder blocks.
Use Blocking
The most effective way to strengthen your floor joists is to use the blocking method.
Most of the time, when the joists are sagging, this is because only one of them has become weakened. By blocking one to the next, you can reinforce it.
To do this, you will need a piece of lumber that is the same thickness as the joists.
The lumber will be installed perpendicularly between the two joists. You will need enough lumber for one row of blocks for every 12 feet of joists.
Strengthen Them With Steel
If you want a long-lasting solution, you can strengthen your joists using a steel plate.
You can either attach the plate to the joist lengthwise to strengthen it or across it. This will depend on how the joist is bending.
It is recommended that you use ½” or ¾” steel for this method. This will give you the best strength possible and will last for many years.
Add a Beam
Much in the same way as using the plate, you can simply add another beam to the one that is sagging.
This is a great way to add some strength and still be able to drill through it for wiring. This method is called “sistering” the joists.
To do this, you will need to use ⅝” carriage bolts and attach the new joists to the side of the old one.
Frequently Asked Questions
How much floor sag is acceptable?
According to most building codes, your floors can only sag less than one inch before they are out of compliance.
While one inch may not seem like much, it will be very noticeable on the floor. If you are noticing any kind of dip in your floors, they could be in violation of the code.
Are sloping floors in older homes normal?
While it is not uncommon for floors to slope in older homes, it should still be fixed.
Sloping floors are an indication that the joists are starting to weaken. This could end up getting worse or could be a sign of a major structural issue.
Can a house settle after 20 years?
Houses will settle over a number of years no matter how well they are built.
For the most part, if a house is settling a few inches, this is an indicator that the soil has eroded. If the home is structurally sound, this shouldn’t present any issues.
Conclusion
If your floor joists need to be strengthened, it is important that you do it as soon as possible.
By using the above methods, you can make sure that your home is safe and structurally sound. You can also be certain that you won’t get any fines from the building inspector.
